The present invention relates to pressure-sensitive adhesive compositions. More particularly the present invention relates to pressure-sensitive adhesives formed from silicone adhesive compositions having excellent tack and adhesive properties.
The term silicone "pressure sensitive adhesive" (PSA) refers to silicone adhesives that adhere to a surface and then are stripped from the surface without transferring more than trace quantities of adhesive to the surface, and can be readhered to the same or another surface because the adhesive retains some or all of its tack and adhesive strength. It is recognized that some surfaces in particular applications form a strong bond with the silicone PSA. In these instance, substrate failure can occur when the PSA is stripped. Generally, however, silicone PSA's exhibit clean removeability.
Silicone PSA's have excellent adhesive and cohesive strength and high tack as well as excellent weatherability, temperature stability, excellent electrical properties and chemical resistance. One use for silicone PSA's are splicing tapes for substrates such as Teflon.RTM. and siliconized surfaces. In coating operations, splicing time is limited, particularly when line speeds are high, so the ability of a silicone PSA to wet out on a surface and then aggressively adhere to it is important. This "on-the-fly" splicing ability of silicone PSA is difficult to measure. Industry-wide tests such as peel adhesion to steel or probe tack adhesion are inadequate for measuring the silicone PSA's performance in application such as splicing. Hence, the loop tack test is selected to demonstrate the ability of a silicone PSA to splice on a selected substrate.
The term "quick stick" refers to a silicon PSA's peel, tack, and loop tack performance. It is desirable to produce a pressure-sensitive adhesive composition exhibiting the ability to adhere to various substrates after a short period of contact.
U.S. Pat. No. 4,309,520, to Blizzard relates to a silicone pressure-sensitive adhesive composition comprising 45-75 parts by weight of a silicone resin and 25-55 parts by weight of a silicone polymer gum, the improvement comprising adding to said composition 0.5 to 50 parts by weight of a cluster compound which contains saterically hindered alkyl groups, based on a total of 100 parts by weight of the resin and polymer gums. These cluster compounds are known in the art.
U.S. Pat. No. 3,992,429, to Knollmueller discloses alkoxysilicone multiple cluster compounds and their preparation.
U.S. Pat. No. 4,077,993, to Knollmueller discloses an improved method for preparing alkoxysilicone multiple cluster compounds.
U.S. Pat. No. 4,058,546 to Knollmueller discloses alkoxysilane double cluster compounds with silicone bridges and their preparation and use.
U.S. Pat. No. 5,190,827, to Lin relates to silicone pressure-sensitive adhesive compositions having high solids contents comprised of a MQ resin, an alkenyl-silicone fluid, and a hydride-silicone fluid. These compositions are cured by a platinum catalyst.
U.S. Pat. Nos. 5,175,058 and 5,096,981 to Traver relate to pressure-sensitive adhesives made from polydioganosiloxanes gum, and requiring the use of primers.
U.S. Pat. No. 3,929,704 to Horning relates to silicone pressure-sensitive adhesive and comprising a silicone resin, a silicone gum and a catalytic amount of a curing agent, said curing agent comprising from about 10 to about 90% by weight of 2,4-dichlorobenzoyl peroxides, a plasticizer and an extender.
U.S. Pat. No. 4,882,377 to Sweet et al, relates to low viscosity pressure-adherent silicone elastomer compositions comprising a mixture of a silicone pressure sensitive composition, a crosslinkable silicone elastomer composition which cure by a chemistry inert to said silicone PSA and a viscosity reducing agent. According to the claim the mixture gives an adhesive with reduced aggressiveness of the adhesive.
All of the above mentioned compositions fail to exhibit the unique combination of quick stick property and peel and tack adhesion as found in the present invention.
It is desirable to provide silicone compositions which upon curing form a pressure sensitive adhesive with the capability to develop rapid and strong adhesion properties to the substrates.
It is further desirable to provide silicone compositions which upon curing form pressure sensitive adhesive tapes with improved loop tack adhesion property while the peel and probe tack adhesions are acceptable. One particular use for the PSA tapes is as splicing tapes.
One aspect of the present invention is the production of silicone PSA's exhibiting a combination of high peel, tack, and excellent loop tack performance.